Multiple switch-board



(No Model.) I

o. E. M GLUER. MULTIPLE SWITGH'BOAED. v No.402,2'64. Patented Apr. 30, 1889.

ill

Scab.

UNITED STATES PATENT OFFICE.

CHARLES E. MOCLUER, OF RICHMOND, VIRGINIA.

MULTIPLE SWITCH-BOARD.

SPECIFICATION forming part of Letters Patent No. 402,264,dated April 30, 1889,

Application filed October 22, 1888. Serial No. 288,878. (No model.) 9

My invention relates to the kind of telephone switch-boards (commonly called multiple switch-boards) found necessary to be provided for the larger telephone-exchanges,

-where the number of subscribers is so large that it is impracticable to concentrate all the subscribers lineterminals within an area so circumscribed as to be within the reach of each individual operator, and at the same time permit of the multiplication of operators which experience has shown to be essential 'to the proper handling of any considerable number of subscriberslines. Such a switch-board is usually composed of a number of sections, each section accommodating one or moreoperators and being practically a duplicate of every other section, each sub scribers line which enters the exchange being connected in series to some kind of a line-terminal or commutating device in each section in such a manner that any individual I shall be' provided with some efficient and reliable means of ascertaining quietly and instantly if the line of any subscriber called for by another subscriber is at that moment connected to the line of any other subscriber on another section of the switch-board, or if it is, as technically expressed, in use. There are two devices usually resorted to for this purpose. One is a test-wire," asdescribed in specification forming part of Let ters Patent No. 305,021, granted to Charles E,

Scribner, of Chicago, Illinois, September 9, 1884. The other is the use of'a central-office indicator operated by a vibrating bell at the subscribers stat-ion, as described in the specification forming part'of Letters Patent No. 319,856, granted to Frank Shaw and William A. Ohilds June 9, 1885. In my deviceboth of these principles are discarded and the same result is accomplished by means which Iwill now proceed to describe with the aid of the accompanying drawing, which represents my device as applied in'part to three sections of a multiple switch-board.

Recurring now to the drawing, which represents a portion only of three sections of a multiple switch-board, P, P, and P are movable connecting-plugs with their metallic points electrically connected to flexible conducting-oords K, K, and K.

IV, \V", and N are metal weights and pulleys looped on the conducting-cords in order to retract the plugs to their normal position upon the table or shelf T, as represented, when they are not in use 0', O, and C are induction-coils.

B is a local battery of any requisitenumber of cells.

V is a vibrator or other circuitrbreaking or,

circuit-varying device, and T is a horizontal 7 table or shelf designed to support the various attachments.

3 and 5 are subscribers stations, connected to commntators at each section-of the switch number of pairs of connecting cords and plugs on any number of switch-board sections.

. Battery 13, vibrator V, and the primaries ofinduction-coils Of, 0, and O are connected up in circuit, one electrode of battery B being connected to one primary terminal of inductioncoil C, while the otherv primary terminal of the same coil is connected to the primary of coil C, and that in like manner to the primary of coil 0 in series. From coil 0' the circuit continues to the vibrator V through its electro-magnet M and contactpoints, and thence to the other electrode of battery B, thus forming a metallic circuit.

The terminals of the secondary coils of the induction-coils C C O are connected to the stationary ends of flexible cords K K K As soon as the local battery-circuit through the primaries of the induction-coils G, C", and C and the vibrator V is completed, the vibrator begins to make and break circuit alternately, thus sending a pulsating current through the primaries of all the inductioncoils connected in circuit. This it will continue to do as long as the strength of the battery and the integrity of the circuit is maintained.

Owing to the fact that in their normal con dition the secondary coils of the inductioncoils are open, of course no inductive electrical effect is experienced; but the moment any single pair of movable connecting-plugs are utilized to connect together the lines of any two subscribers the secondary circuit is closed and an induced intermittent current of electricity is caused to flow in the closed circuit thus formed by the secondary of the induction-coil, the flexible cords and plugs, the two subscribers lines and their station appliances, and the earth, to which the distant terminals of the subscribers lines are of course connected. By properly graduating the strength of the local battery I can manifestly regulate the strength of the induced current flowing through the secondary coils and over the subscribers lines, so that, although the beat or tick of the induced intermittent current can be plainly heard in the telephones of the subscribers, it will not interfere in the slightest degree with their conversation, being but a little louder than the ticking of an ordinary watch when held to the ear.

I prefer that the indication line in use should be conveyed to the ear of the switchboard operator through the medium of a special movable plug, 0, connected by a flexible cord to one side of her head-telephone H, and thence to earth, as described in specification of Patent No. 305,021 before alluded to; but the indication may be conveyed to the eye of the operator by the movement of a galvanometer-needle, or to the ear, as well, by the movement of the armature of a delicate polarized relay, which will readily respond to the electrical impulses of alternating polarity flowing in the secondary circuit in consequence of the regular opening and closing of the primary circuit by the circuit-breaker.

It now an operator at section No. 1, Fig. 1, of the multiple switch-board is asked by subscriber No. 5 to connect him to another subscriber-say No. 8she will, before respondg to his order, place her testing-plug 0 mo- 1 mentarily upon the thimble or jack-knife switch or other commutator representing the switch-board terminal of No. 3s line on her section. If she does not hear the indication line in use, she will make the connection by carrying movable plugs P P to the thimbles representing the terminals of subscribers lines Nos. 3 and 5, thus connecting them together through the plugs and cords, and the secondary of their individual induction-coil enabling the two subscribers to communicate, but at the same time completing the secondary coil-circuit and causing the current induced by the local or primary battery-current to flow out over the two lines. If now, while subscribers lines Nos. 3 and 5 are thus connected together at the switch-board section No, 1, another subscriber asks an operator at any othersectionsay No. 3-to connect him to subscriber No. 5, she will first apply her testplug to the switch-board terminal of subscribers line No. 5, thus providing for the intermittent induced current flowing over lines 3 and 5 another path to the earth through her head-phone and producing in her ear the regular ticking due to the opening and closing of the primary local circuit through the induction-coil by which Nos. 3 and 5 are connected together on section No. 1, thus indicating to her practiced ear instantly that No. 5 is in use, and she will so inform the calling subscriber orally or by signal. Had No. 5 not been in use, that fact would have been just as instantaneously indicated by the absence of the noise or sound due to the action of the battery B, vibrator V, and induction-coil 0. Had a connection been ordered with No. 3 instead of N o. 5, the mode of testing would have been similar, the test-plug 0 being placed on the terminal to subscribers line No. 3, however, instead of No. 5.

Instead of the vibrator or circuit-breaker being adjusted to open and close the circuit at a moderate rate of speed, so as to produce in the telephones a ticking noise similar to that of awatch, it may be adjusted to beat so rapidly that a musical tone will result.

Although compelled to make use of them in connection with my device, I disclaim the movable plugs,weights, and pulleys,orweights and tubes, circuit-breaker, and arrangement of head-phone and test-plug as being my invention, those being old and well-known devices.

I do claim as my invention, however, upon which I desire to secure Letters Patent- 1. The combinatiomwith a multiple switchboard and connected telephone-lines, of a testing apparatus comprising a local circuit with a battery and rheotome, said local circuit passing through the primaries of the induction-coils at each board, the terminals of the secondary of each induction-coil being connected to the switch-plugs of a flexible cord, with a testing-plug grounded through a receiver, as described.

2. The combination, with a telephone-ex change multiple switch-board, of a local battery, a rheotome, and the primaries of a series of Ruhmkorif induction-coils connected up in metallic circuit, While the terminals of the secondaries of the induction-coils are connected each to a pair of flexible connecting .cords and plugs, as described.

3. The combination of any number of Ruhmkorif induction-coils, with their primaries connected up in circuit with a local battery,

and a vibrator or circuit-breaker for each circuit, thereby producing an intermittent or undulatory flow of electricity through the said primary coils, the secondary terminals of each induction-coil being connected to a separate pair of connecting cords and plugs in such manner that the necessary movement of the connecting-plugs when carried by the hand of the operator to the line-commutators in the act of making a connection will not disconnect them, but Will cause an intermit- "tent or undulatory fiow of induced electricity to traverse the subscribers lines thus connected together until they are disconnected,

substantially as described, and for the purpose explained in the foregoing specification.

CHARLES E. MOCLUER.

Witnesses: V

WILLIAM R. PARRY, J OHN W. LAIRD. 

